The present invention relates broadly to security apparatus for dispensing devices and, more particularly, to an electrical circuit to detect tampering with a fuel dispenser totalizer and a method associated therewith.
Liquid fuel, such as gasoline, is a fungible, flowable material, which is usually transferred between several differently sized vessels in varying amounts prior to its ultimate use. Accordingly, accurate measurements of the quantity of fuel transferred are a requirement for proper inventory control. Fuel dispensers control and meter the flow of fuel therefrom and account for each unit dispensed. Fuel, particularly gasoline and diesel fuel, dispensed from commercial outlets is stored in underground tanks which are periodically replenished as fuel is drained therefrom. Therefore, not only do individual purchases have to be totaled, a running total of fuel dispensed from any given dispenser must be maintained. Therefore, a "totalizer" is used to keep such a running total of fuel dispensed. The totalizer is typically an electromechanical device that uses a solenoid to advance a mechanical counter one increment for each unit of fuel dispensed. All the individual station owners monitor their sales through individual sales, the fuel distributor must monitor the running total to maintain an accurate assessment of fuel dispensed.
Situations can arise where less than honest individuals can disable the totalizer, indicating that less fuel was moved through the dispenser than was actually dispensed, resulting in fraudulent operation, and a loss to the fuel supplier. As may be expected, if the totalizer indicates that less fuel was dispensed than was actually dispensed, whomever is operating the pump will realize an unfair profit. Further, the totalizers must be depended on for accurate dispensing information for billing and predictions of future fuel requirements.
As previously stated, the totalizer is typically an electromechanical device which is operated by a solenoid. In modern fuel dispensers, the solenoid is microprocessor controlled as is virtually all other aspects of fuel dispenser operation. The microprocessor will receive an input from a fuel metering device and will then in turn instruct the solenoid to advance the counter one unit. Therefore, for every unit dispensed, the solenoid is activated to advance a counter. The solenoid, being a coil of wire surrounding a magnet will emit a magnetic pulse each time it is energized for advancing the counter. Therefore, for each unit dispensed, an electromagnetic pulse will be emitted from the solenoid operating the counter. As may be expected, if multiple products are collectively arranged, there will be a totalizer for each product and a corresponding magnetic pulse for each unit of fuel dispensed by each product. This circuit arrangement is illustrated in FIG. 1.
A current, common method of detecting tampering with a totalizer involves detecting when the counter is actually disconnected. This circuit arrangment is illustrated in FIG. 2. There, a connection to ground or power is sent out to each counter and then looped back to the microprocessor input port through lines 44,46. There may be one signal for each totalizer, as illustrated in FIG. 2, or all the totalizers may be wired together. The microprocessor monitors the input port as long as the input is of the proper polarity, it assumes that the counter is functioning properly. Thus, the microprocessor has no way of knowing if the solenoid was activated, if the counter solenoid is operational or if the wires to the coil have been disconnected. All that can be determined is whether power is available. As may be expected, this method does not completely allow the determination of whether the counter is operational.